This invention relates generally to a current source circuitry, and more particularly to a circuit for generating a reference current which is proportional over temperature to the ratio of the pinch-off voltage (V.sub.P) of a standard junction field effect transistor (JFET) to some resistance.
As is well known, the pinch off voltage V.sub.P is the voltage at which there is substantially zero source-to-drain current in a JFET. That is, no current will flow in the JFET if the JFET's gate is pulled high enough in voltage with respect to its source. Up to now, this could be accomplished only by using a very large area JFET and placing a large resistance between its gate and source terminals.
A reduction in the size of the JFET has been accomplished by incorporating into the circuit a large NPN transistor and a diode. In either event, large devices have been necessary which occupy a significant amount of die area.